Pomegranate peel-derived nanocellulose and polyphenol extract for active packaging: Combined effects with γ- and low-energy X-ray irradiation in ready-to-eat ham preservation.

Abstract

Pomegranate peel, an industrial by-product, was valorized as a source of polyphenols and cellulose derivatives, including cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), to develop bioactive nanocomposite films. Extracts from three varieties, Bni Khaled (PPBK), Gabsi (PPG), and Ghardimaa (PPGD) were screened, and the PPG extract exhibited the highest antioxidant activity (IC₅₀: 0.08 mg/mL) and antimicrobial activity (MIC: 0.25-4 mg/mL), leading to its selection for film incorporation. The films, based on poly (butylene succinate) (PBS), starch, and tributyl citrate (TBC), were produced by melt extrusion (150 °C, 2 min). The incorporation of CNCs or CNFs reduced oxygen permeability by 61 and 45%, respectively, and increased tensile strength by 8% and 16.5%, respectively, while elongation at break decreased by more than 90%. The films containing PPG extract showed antimicrobial activity against Listeria monocytogenes, Staphylococcus aureus, Salmonella Typhimurium and Escherichia coli. In situ application on ready-to-eat (RTE) ham demonstrated that combining active films with irradiation produced enhanced antimicrobial activity compared with either treatment alone. Low-energy X-rays were more effective than γ-irradiation, achieving a 2.75 log CFU/g reduction in total viable count and complete inhibition of L. monocytogenes within 3 days, compared to a 1.02 log CFU/g reduction under γ-irradiation. Significant reductions were also observed for lactic acid bacteria (up to 1.63 log CFU/g) and for yeasts and molds, with complete inhibition under X-ray combined treatments. These findings demonstrate that integrating nanocomposite films with low-dose irradiation constitutes an effective strategy to enhance microbial safety and extend the shelf life of RTE ham products.